Questions of application of fiber-optic sensors for monitoring crack growth during rock deformations

The paper considers ways to solve the problem of developing a system for monitoring displacement in quarries, which are the main main cause of the collapse of boards and berms in quarries. To ensure safety and constant monitoring during work at the quarry, there are chiseled fiber-optic sensors. The fiber-optic sensor is made on the basis of a single-mode optical fiber, which makes it possible to measure the displacements of the mountain range at distances of about 30 km with high accuracy. Laboratory sample a fiber-optic sensor in its work uses a method for monitoring additional losses that occur during mechanical action on an optical fiber. The fiber-optic sensor was made to show a fairly high linearity and accuracy during measurements and can be used to control the deformation of the array after appropriate refinement of its design. This article is aimed at creating means of controlling the process of deformation and displacement of a mountain massif. Ultimately, the results of the study will help prevent accidents associated with the collapse of the sides. Since the growth of cracks in the rocks of the bort mountain massif leads to its sudden collapse and creates a significant danger for personnel, it also causes the failure of mining equipment.

Segment tip geometry of sheet intrusions, II: Field observations of tip geometries and a model for evolving emplacement mechanisms

Igneous sheet intrusions are segmented across several orders of magnitude, with segment tip geometry commonly considered indicative of the propagation mechanism (brittle or non-brittle). Proposed propagation mechanisms are inferred to represent host rock mechanical properties during initial magma emplacement; typically, these models do not account for segment sets that show a range of tip geometries within the same lithology. We present a detailed structural characterization of basaltic sill segments and their associated host rock deformation from the Little Minch Sill Complex, Isle of Skye, UK, and a broader comparison with segment geometries in three additional intrusive suites (Utah, USA; and Mull and Orkney, UK). Each separate host lithology shows multiple tip geometries and styles of host rock deformation, from elastic-brittle fracture, to viscous indentation and fluidisation. We attribute this range of host rock deformations to evolving conditions that occur at the tips both during sheet growth and arrest.

Instability Assessment of Hanging Wall Rocks during Underground Mining of Iron Ores

The paper presents the study of the deformation processes development in unstable rocks of the hanging wall during mining a thick steeply dipping ore deposit in the example of the Yuzhno-Belozerskyi deposit. In the studied field, there are problems of stability of hanging wall rocks, represented by low-resistant shale rocks that do not withstand significant outcrops in time. A decrease in stability is manifested in the form of failure of the hanging wall rocks into the stope. Based on a detailed study of the ore deposit geological structure and the performance of the stopes mining, according to the survey data, an area of the deposit has been identified where the ore failure and dilution reach 4%–8% with a maximum value of 12%. This also makes it possible to determine the most important averaged source data for performing physical modeling on equivalent materials. It has been determined that the deformation value of the hanging wall rocks with subsequent failure into the stope and ore mass deformation in the sloping bottom change exponentially with an increase in the depth of the stope location, and the dynamics of increasing rock deformations in the hanging wall is noticeably higher than in the sloping bottom of the stope. This reduces the quality of the mined ore and increases the probability of rock failure area propagation to the hanging wall drifts with their subsequent destruction. The results of physical modeling are characterised by acceptable reliability and are confirmed by a high similarity with the actual data on ore dilution with broken rocks during the stopes development. It has been found that during the formation of a steeply dipping outcrop of stopes with an area of 1200 m2, unstable rocks of the hanging wall are prone to failure of significant volumes. For successful mining and achieving stope element stability, it is recommended to optimise its parameters, the height, width and the value of a steeply dipping outcrop, as well as to preserve the ore pillar in the hanging wall until the ore is broken and drawn from the rest of the stope.

FLUID INFLUX TO A BATTERY OFINCOMPLETE HORIZONTALLY BRANCHED WELLS IN DEFORMED FORMATION

Using numerousexperimentalandfield researches, it was established that there are rock deformations duringoil and gas fields development, occurred due to thereservoir response. It has been established that formationvolume of pore space is decreased due to elastic expansion of rock grains and increase of compression strength transferred to matrix from mass of overlying rocks due to formation pressure depletion. As the result, there are deformation processes in porous medium accompanied by degradation of its porosity and permeability, and suffered greater change compared to the formation porosity, sufferedpermeability at the samepressure variation. Demonstration of mentioned anomalies under formation conditions leading to non-linear effect can strongly influence the whole process of the reservoir development and lead to various qualitative and quantitative differences between the observed facts and the indicators which were calculated using standard methods. Formulas for determination of debits of incomplete horizontally branched wells (HBW) in deformed formation for various number of horizontal shafts in a battery were obtained in this work using image method of drains (sources) and superposition. Obtainedestimate indicatorscan be used inengineering works during development of the deposits indeformed environment.

Deformation of the Earth’s crust: measurement methods, regularities, nature

Research subject. This paper investigates rock deformations and stress states in mineral excavation sites.Materials and research methods. On the basis of a 20-year geodeformational monitoring of natural stresses and deformations in the rock mass at mining sites in the Urals, carried out by the Laboratory of Geodynamics and Rock Pressure at the Institute of Geology and Geology of the Ural Branch of the Russian Academy of Sciences, we propose a novel structure of natural stress fields with reference to their change over time. Measuring instruments should be calibrated using standards of length and weight, including surveying tape measures, tapes, wires of various chemical composition, light and radio-range finders.Results. For the mining sites under study, the parameters of the variable component of stress fields with a chronological reference were determined, along with a forecast of loads both during preparatory and mining stages up to 2022. The experiments showed that, along with lithostatic (gravitational) and tectonic stresses, it is necessary to distinguish variable “astrophysical” rock stresses due to the cyclic expansion and contraction of the Earth.Conclusions. Using available measurements obtained during the most recent 11-year nanocycle of solar activity, regularities in the formation of rock deformations and stresses were revealed. A forecast of natural stresses with an increase in variable “astrophysical” stresses in the upcoming solar activity cycle was made. Measurements of rock deformations are currently performed using methods based on various physical principles. The results obtained thus far are relative, not permitting to judge about absolute values. The numerical values of dozens of fundamental physical constants are also variable. The international community of scientists should develop a mechanism to track changes in their magnitude over time.

Fully Coupled Stochastic Geomechanical-Geochemical - Reservoir Modeling for Fracture Reservoirs

Carbonate reservoirs contain a significant portion of the world's oil reserves. The uptake of oil from these reservoirs is difficult due to the complex hydro-thermo-geomechanical-geochemical processes. In recent years many efforts have been made to model these processes in fractured rocks. A few studies have been done on the stochastic nature of these processes. Geomechanical models need to take into account the reservoir rock deformations that are the result of the pores and fracture pressure, while geochemical models deal with the chemical reactions that take place into fracture and matrix with their principal processes such dissolution and precipitation. In this paper we will make the modeling from the stochastic point of view of these processes by making a model to deal with such parameters and coefficients that are stochastic, seeing them as random variables. In our knowledge this is the first work of this kind. From the geomechanical point of view we will use the stochastic nature of the Biot linear model with uncertain coefficients, while for the stochastic geochemical model we will use the Langrazhian formulation.

Remote thermal detection of exfoliation sheet deformation

A growing body of research indicates that rock slope failures, particularly from exfoliating cliffs, are promoted by rock deformations induced by daily temperature cycles. Although previous research has described how these deformations occur, full three-dimensional monitoring of both the deformations and the associated temperature changes has not yet been performed. Here we use integrated terrestrial laser scanning (TLS) and infrared thermography (IRT) techniques to monitor daily deformations of two granitic exfoliating cliffs in Yosemite National Park (CA, USA). At one cliff, we employed TLS and IRT in conjunction with in situ instrumentation to confirm previously documented behavior of an exfoliated rock sheet, which experiences daily closing and opening of the exfoliation fracture during rock cooling and heating, respectively, with a few hours delay from the minimum and maximum temperatures. The most deformed portion of the sheet coincides with the area where both the fracture aperture and the temperature variations are greatest. With the general deformation and temperature relations established, we then employed IRT at a second cliff, where we remotely detected and identified 11 exfoliation sheets that displayed those general thermal relations. TLS measurements then subsequently confirmed the deformation patterns of these sheets showing that sheets with larger apertures are more likely to display larger thermal-related deformations. Our high-frequency monitoring shows how coupled TLS and IRT allows for remote detection of thermally induced deformations and, importantly, how IRT could potentially be used on its own to identify partially detached exfoliation sheets capable of large-scale deformation. These results offer a new and efficient approach for investigating potential rockfall sources on exfoliating cliffs.

40Ar/39Ar age of rock deformations across the Bazhenov suture zone (eastern border of the Middle Urals)

Research subject. This article presents data on the nature of rock deformations in the Bazhenov suture zone. The data was obtained by 40Ar/39Ar dating of mica samples from schists and blastomylonites, which were collected acrossan area extending approximately for 100 km along the Bazhenov suture. This suture separates the Eastern zone of the Middle Urals dipped under the cover of the West Siberian plate from exposed geologic structures of the Urals.Methods.The character of the deformations was studied by means of direct geological observation. The age of the deformations was determined by mica dating using the 40Ar/39Ar method.Results. The deformations were found to have occurred in several phases. The initial phase, which led to the formation of a band of blastomylonites and rocks showing a varying degree of schistosity with a width of over 10 km in particular areas, is likely to have had the character of left-lateral fault. The upper age limit of this deformation phase is determined by the intrusion of the subalkaline rocks of the Petukhovskii complex (280 Ma), which had not been affected by any deformation processes. The subsequent type of deformations had been left-lateral strike-slip faults of submeridianal strike and subvertical dip, which were represented by low-thickness (usually about 10 cm, rarely up to 0.5 m) zones of intensely deformed rocks cutting the schistosity of the previous phase at an acute angle. The final phase of the deformations is shown to be a sloping fault. The dislocation planes of this type were represented by slickensides and chlorite incrustations. Despite the apparent polychronicity of the deformation processes, which were established within the Bazhenov suture zone by our geological observations, 40Ar/39Ar age dating identified only one event. The average value of five conducted tests was about 251 Ma. Apparently, this age should be associated with the most recent geological processes having occurred at temperatures sufficient to fully overload the K-Ar isotopic system of the studied rocks, such as the deformations caused by strike-slip dislocations.Conclusions. The strike-slip fault dislocations dated in this work occurred approximately 25 Ma after the completion of the tectonic activity in the Serov-Mauk fault zone, which is located to the west of the Bazhenov zone. In addition, the time of these dislocations very nearly coincides with that of the formation of the grabens of meridional strike at the base of the West Siberian plate, which took place about 250 Ma ago. This supports apreviously made conclusionon the similar character of the geological development of the eastern border part of the Urals and the adjoining basement of the West Siberian plate.